Field of the Invention
This invention relates to an improvement in the process of extracting metals, particularly copper, from aqueous ammoniacal solutions employing as the extractants beta-diketone compounds dissolved in a water immiscible hydrocarbon diluent. In particular, the improvement comprises the use of electrostatic coalescers to control entrainment of the aqueous phase in the organic extractant phase to significantly reduce metal production costs and to provide improved metal quality recovery by minimizing ammonia entrainment and carry over to the aqueous stripping solution from which the metal is recovered, typically by electrowinning of the aqueous strip solution in a tankhouse.
Beta-diketones are typically employed to extract a metal, such as copper, from aqueous ammoniacal leach liquors. A typical circuit involves two stages of extraction, a wash stage and one to two stripping stages with an aqueous acid stripping solution. Entrainment of the ammoniacal aqueous phase in the organic, and carry over to the stripping solution from which the metal is eventually recovered, results in higher metal production costs and poorer quality of the metal recovered.
Electrostatic coalescers have been employed in the past to break water in oil emulsions in the oilfields. Such coalescers have been employed in an attempt to reduce aqueous entrainment in a process of extracting copper from aqueous acidic leach solutions. Such systems from acid leach solutions, do not however pose the problems associated with ammoniacal solution entrainment, and accordingly do not solve all the entrainment problems posed in extraction of metals, particularly copper, from aqueous ammoniacal solutions.